Thalassocyon is a genus of sea snails, marine gastropod molluscs in the family Thalassocyonidae.
Riedel (1995) elevated this genus to a family level (Thalassocyonidae), a vision not supported in Verhaeghe & Poppe (2000), nor in Bouchet, Rocroi et al. (2005)
This genus is found from South Africa to the Kermadec Islands and the North Island of New Zealand.